FIG. 1 illustrates part of an apparatus used for conventional robotic surgery. The apparatus comprises a robot arm 1, only the distal end of which is shown in FIG. 1. A rail 2 extends from the distal end of the arm towards a patient, whose skin is indicated at 3. At the end of the rail is a surgical instrument 4 which passes into the patient for performing surgery. The instrument enters the patient through an incision in the skin. To keep the incision clear, and to avoid the patient's skin being torn when the instrument is moved, a port 5 is located in the incision. The port is carried by the rail 2. The port is free to slide along the length of the rail as indicated by arrow 6, and the port clips into the incision. Because the port adheres to the tissue around the incision, when the robot arm 1 moves the instrument into and out of the patient during surgery a force is applied to the port. This force moves the port along the rail so that the port can stay in place in the incision.
This approach has a number of problems. First, the port needs some mechanism to bind to the incision in order that it will stay in place when the instrument is moved. This mechanism can enlarge the incision or cause damage to the tissue around the incision. Second, if the port is not properly secure in the incision it can be ripped out of the incision when the robot moves the instrument. This can again damage the incision. Finally, the mechanism relies on forces being applied to the port by the tissue around the incision. These forces can themselves cause damage to the tissue at the incision.
Similar problems arise in non-robotic laparoscopic surgery. However, in manual surgery the surgeon is standing next to the patient and can normally see or feel the signs of a port becoming loose or of excessive force being applied to the port. In robotic surgery the force feedback that a surgeon gets from a robot may be comparatively weak or imprecise, and with many other displays to look at the surgeon might not keep the ports under constant observation.
There is a need for an improved way of locating surgical ports.